/*
 * Template.java February 2001
 *
 * Copyright (C) 2001, Niall Gallagher <niallg@users.sf.net>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */

package wx.xml.simpleframework.xml.core;

/**
 * This is primarily used to replace the <code>StringBuffer</code>
 * class, as a way for the <code>TemplateEngine</code> to store the
 * data for a specific region within the parse data that constitutes
 * a desired value. The methods are not synchronized so it enables
 * the characters to be taken quicker than the string buffer class.
 *
 * @author Niall Gallagher
 */
class Template {

    /**
     * This is used to quicken <code>toString</code>.
     */
    protected String cache;

    /**
     * The characters that this buffer has accumulated.
     */
    protected char[] buf;

    /**
     * This is the number of characters this has stored.
     */
    protected int count;

    /**
     * Constructor for <code>Template</code>. The default
     * <code>Template</code> stores 16 characters before a
     * <code>resize</code> is needed to append extra characters.
     */
    public Template() {
        this(16);
    }

    /**
     * This creates a <code>Template</code> with a specific
     * default size. The buffer will be created the with the
     * length specified. The <code>Template</code> can grow
     * to accomodate a collection of characters larger the the
     * size spacified.
     *
     * @param size initial size of this <code>Template</code>
     */
    public Template(int size) {
        this.buf = new char[size];
    }

    /**
     * This will add a <code>char</code> to the end of the buffer.
     * The buffer will not overflow with repeated uses of the
     * <code>append</code>, it uses an <code>ensureCapacity</code>
     * method which will allow the buffer to dynamically grow in
     * size to accomodate more characters.
     *
     * @param c the <code>char</code> to be appended
     */
    public void append(char c) {
        ensureCapacity(count + 1);
        buf[count++] = c;
    }

    /**
     * This will add a <code>String</code> to the end of the buffer.
     * The buffer will not overflow with repeated uses of the
     * <code>append</code>, it uses an <code>ensureCapacity</code>
     * method which will allow the buffer to dynamically grow in
     * size to accomodate large <code>String</code> objects.
     *
     * @param str the <code>String</code> to be appended to this
     */
    public void append(String str) {
        ensureCapacity(count + str.length());
        str.getChars(0, str.length(), buf, count);
        count += str.length();
    }

    /**
     * This will add a <code>Template</code> to the end of this.
     * The buffer will not overflow with repeated uses of the
     * <code>append</code>, it uses an <code>ensureCapacity</code>
     * method which will allow the buffer to dynamically grow in
     * size to accomodate large <code>Template</code> objects.
     *
     * @param text the <code>Template</code> to be appended
     */
    public void append(Template text) {
        append(text.buf, 0, text.count);
    }

    /**
     * This will add a <code>char</code> to the end of the buffer.
     * The buffer will not overflow with repeated uses of the
     * <code>append</code>, it uses an <code>ensureCapacity</code>
     * method which will allow the buffer to dynamically grow in
     * size to accomodate large <code>char</code> arrays.
     *
     * @param c   the <code>char</code> array to be appended to this
     * @param off the read offset for the array
     * @param len the number of characters to append to this
     */
    public void append(char[] c, int off, int len) {
        ensureCapacity(count + len);
        System.arraycopy(c, off, buf, count, len);
        count += len;
    }

    /**
     * This will add a <code>String</code> to the end of the buffer.
     * The buffer will not overflow with repeated uses of the
     * <code>append</code>, it uses an <code>ensureCapacity</code>
     * method which will allow the buffer to dynamically grow in
     * size to accomodate large <code>String</code> objects.
     *
     * @param str the <code>String</code> to be appended to this
     * @param off the read offset for the <code>String</code>
     * @param len the number of characters to append to this
     */
    public void append(String str, int off, int len) {
        ensureCapacity(count + len);
        str.getChars(off, len, buf, count);
        count += len;
    }


    /**
     * This will add a <code>Template</code> to the end of this.
     * The buffer will not overflow with repeated uses of the
     * <code>append</code>, it uses an <code>ensureCapacity</code>
     * method which will allow the buffer to dynamically grow in
     * size to accomodate large <code>Template</code> objects.
     *
     * @param text the <code>Template</code> to be appended
     * @param off  the read offset for the <code>Template</code>
     * @param len  the number of characters to append to this
     */
    public void append(Template text, int off, int len) {
        append(text.buf, off, len);
    }

    /**
     * This ensure that there is enough space in the buffer to allow
     * for more characters to be added. If the buffer is already
     * larger than min then the buffer will not be expanded at all.
     *
     * @param min the minimum size needed for this buffer
     */
    protected void ensureCapacity(int min) {
        if (buf.length < min) {
            int    size = buf.length * 2;
            int    max  = Math.max(min, size);
            char[] temp = new char[max];
            System.arraycopy(buf, 0, temp, 0, count);
            buf = temp;
        }
    }

    /**
     * This will empty the <code>Template</code> so that the
     * <code>toString</code> paramater will return <code>null</code>.
     * This is used so that the same <code>Template</code> can be
     * recycled for different tokens.
     */
    public void clear() {
        cache = null;
        count = 0;
    }

    /**
     * This will return the number of bytes that have been appended
     * to the <code>Template</code>. This will return zero after
     * the clear method has been invoked.
     *
     * @return the number of characters within this buffer object
     */
    public int length() {
        return count;
    }

    /**
     * This will return the characters that have been appended to the
     * <code>Template</code> as a <code>String</code> object.
     * If the <code>String</code> object has been created before then
     * a cached <code>String</code> object will be returned. This
     * method will return <code>null</code> after clear is invoked.
     *
     * @return the characters appended as a <code>String</code>
     */
    public String toString() {
        return new String(buf, 0, count);
    }
}   
